1. Field of the Invention
The invention relates to a device for automatically resetting the play between a brake lining and a rotary brake member associated with a wheel to be braked.
More specifically the invention relates to such a brake play resetting device comprising an adjusting member which during braking is adapted to move out of an initial position and to return thereto when the braking force is discontinued and which during braking under the action of a pressure cylinder actuator produces braking contact between the brake lining and said member to be braked, and is provided with a member, forming part of a unidirectional coupling means, which is adapted to pivot in relation to the adjusting member on contact with an abutment, said coupling being adapted to turn a setting shaft (which is causes adjustment by spiral flanks and transmits the braking force) when a rated play amount between the parts to be braked is exceeded, in a direction effective to produce a reset effect to reduce said play, and with an axial compression spring between the setting shaft and the adjustment means, and which, when during braking a certain braking force is exceeded, yields and enables an axial displacement of the setting shaft to take place between two abutments on said adjustment means and in so doing causes disengagement between the setting shaft and the pivoting member by means of a coupling member equipped with a conical surface, said coupling member having oblique flanks cooperating with oblique flanks of the setting shaft in order to maintain the unidirectional coupling function of the pivoting member.
2. Description of Prior Art
Such a device is described in the German patent No. 2,443,003 although here the system is limited to linkage setting members and does not have any wide definition envisaging other types of devices for enabling play resetting to take place. The present invention is however not limited to linkage adjustment means. However, in the following description the problem addressed by the invention is explained in the context of a conventional linkage setting member.
Thus for instance the German pre-examination specification No. 2,008,139 describes a linkage adjustment means enabling the additional play, due to wear, between a brake drum and brake shoes to be taken up in steps or continuously by resetting leading to a reduction thereof.
Linkage adjustment means have also be proposed, see the U.S. Pat. No. 3,351,163 or, respectively, the German examined specification 1,480,038, which when a certain braking force has been exceeded, override a readjustment function so that an excessive reset is precluded.
However, not one of these prior art references discloses a device capable of taking into account the effects of brake parts which have been heated by repeated vigorous braking and thus avoid excessive reset caused thereby. Such excessive reset may in extreme cases lead to seizing of the brake members.